The present invention relates to a method and an apparatus for predicting the recovery time of a hard disk drive power supply from a waiting state in a system provided with the hard disk drive.
Usually, in a system provided with a hard disk drive, the priority of each read/write task in the hard disk drive is high and accordingly, each task requires a fast response. However, once the hard disk drive stops its spindle motor and unloads the actuator so as to save power, the hard disk drive takes a long time to restore the spindle motor and the actuator to a usable state.
That is, if a host system transmits a power save command to the a hard disk drive, the hard disk drive enters a stand-by mode or a sleep mode in response to the received command. In the stand-by mode, only the interface circuit of the host system is active, so that the host system can receive commands. However, all other components of the host system are in a power-off state. In the sleep mode, all the operations of the host system enter the power-off state. To be restored from this mode, the host system receives a hard reset command or a soft reset command. The time required until the host system exits the stand-by or sleep mode to enter an idle mode or execute a read/write operation is considered as a recovery time, mainly consisting of the time it takes until the spindle motor reaches a predetermined rotation speed (also referred to as a time required for restarting the spindle motor) and the time required until the actuator is released from an unloaded position so as to calibrate the servo, then moved to a predetermined cylinder (also referred to as a time required for moving the actuator to a predetermined cylinder). So far, this recovery time of the power supply has been long.
In a system provided with a conventional hard disk drive, the host system had to wait without executing any task during a period of time between when the hard disk drive was restored from a stand-by state for power saving (for example, the spindle motor was stopped and the actuator was unloaded) to a usable state. Consequently, the time required for restoration from a stand-by state was wasteful. It took several seconds until the spindle motor was restarted in some cases. This has been a serious problem for hard disk drives for which fast responses are expected.
Under such circumstances, it is an object of the present invention to provide a method and an apparatus for predicting a recovery time, to be employed in a system provided with a hard disk drive that can solve the above conventional problems and speed up the processing in the whole system provided with such a hard disk drive with efficient use of a recovery time of the power supply to restore from a stand-by state, as well as a hard disk drive that uses the method.